Overweight Dogs Don't Live as Long, and Scientists Have Calculated How Much Less

Research on 12 popular dog breeds finds the average difference in life span between normal weight and overweight or obese dogs, and it makes for worrying reading.

Overweight dogs have shorter lives, and scientists have calculated by how much. The effects are worse for small dogs like the Yorkshire Terrier, pictured, showing the importance of keeping your dog to a normal weight. If in doubt, as your vet.
Photo: Caz Harris Photography/Shutterstock

By Zazie Todd, PhD

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We know that being overweight or obese is bad for pet dogs, but just how bad is it?

For the first time, scientists have worked out the difference in average life span for normal weight and overweight pet dogs of 12 breeds. The study by Carina Salt (WALTHAM Centre for Pet Nutrition) et al. is published in the Journal of Veterinary Internal Medicine.

The scientists looked at some of the most popular breeds of all sizes, from Chihuahuas and Pomeranians to Golden Retrievers and German Shepherds.

The study only looked at dogs that have been spayed or neutered.

Co-author Prof. Alex German (University of Liverpool) told Science  Daily,
"Owners are often unaware that their dog is overweight, and many may not realise the impact that it can have on health. What they may not know is that, if their beloved pet is too heavy, they are more likely to suffer from other problems such as joint disease, breathing issues, and certain types of cancer, as well as having a poorer quality of life. These health and wellbeing issues can significantly impact how long they live."

The biggest differences in life span were found for little dogs. For a normal-weight male Yorkshire Terrier, the average life span is 16.2. However, if the dog is overweight, the average life span is 13.7 – a reduction of 2 and a half years. This was the largest difference found.

Big dogs had a smaller difference, but still had a reduced lifespan if they were overweight. A normal-weight male German Shepherd lives for 12.5 years, whereas his overweight counterpart only lives 12.1 years on average. This was the smallest difference found in the study.

"Most pet owners feel that dogs’ lives are too short as it is. This data shows how serious the effect of being overweight is on dogs"

The corresponding figures for female German Shepherds are 13.1 and 12.5 years, respectively, while for female Yorkshire Terriers the average lifespan is 15.5 if normal weight and 13.5 if overweight.
Amongst medium size dogs, a male Beagle of normal weight lives 15.2 years and his overweight counterpart lives only 13.2 years. For female Beagles, those of normal weight have a life span of 15.3 compared to 13.3 for those who are overweight.

The breeds included in the study were the Yorkshire Terrier, Pomeranian, Chihuahua, Shih Tzu, American Cocker Spaniel, Dachshund, Beagle, Pit Bull, Boxer, Golden Retriever, Labrador Retriever and German Shepherd.

The results are shown in the table below.

The life span of overweight dogs compared to normal weight dogs for 12 breeds. The effects of being overweight are worse for small dogs than large dogs.
Average life span for normal and overweight dogs. Reproduced from Salt et al (2019) under Creative Commons licence.

The researchers looked at anonymized data from BANFIELD Pet Hospitals (almost all in the US) from 1994 to 2015. Normal weight and overweight dogs of the 12 breeds in the study were matched at around age 7.5 for the purposes of analysis.

The dog’s weight was assessed by a 5-point Body Condition Score from 2010, and on a 3-point scale before then. In the analysis, dogs were classified as either underweight, overweight, or a normal weight.

The study included data from over 50,000 dogs. Although only 12 popular breeds were considered, it seems likely that the results would also apply to other breeds.

Overweight dogs have a shorter life span, and this post shows how much shorter for 12 popular dog breeds. Photo shows a spaniel in the trunk of a car after a walk.
Photo: Josh Powell/Shutterstock

This research cannot explain why overweight dogs tend to have a shorter life. As well, we have to remember that dogs typically don’t have a natural death but are often euthanized due to quality of life issues, and treatment costs may play a role in that if people are unable to afford treatment.

The study data covers a long time period, and there have been medical advances in this time.

Nonetheless, the results show that if your dog is overweight, it would be wise to do something about it.

Many owners find it difficult to judge if their dog is a normal weight or not, and it is also easy to be in denial about this. If you are not sure, ask your veterinarian. If your dog is overweight, speak to your vet about the best ways to get your dog down to a normal weight.

Research also shows that owners of overweight dogs need to change their own behaviour. Strategies that may be useful include setting specific goals for behaviours (such as how far you will walk the dog) and outcomes, as well as considering strategies to use to help you manage your dog’s food intake.

I think most pet owners feel that dogs’ lives are too short as it is. This data shows how serious the effect of being overweight is on dogs, and therefore how important it is to maintain your dog’s weight at a normal level.

The paper is open access (link below).

If you like this post, check out my book Wag: The Science of Making Your Dog Happy. Modern Dog magazine calls it "the must-have guide to improving your dog's life."

Zazie Todd, PhD, is the award-winning author of Wag: The Science of Making Your Dog Happy and Purr: The Science of Making Your Cat Happy. She is the creator of the popular blog, Companion Animal Psychology, writes The Pawsitive Post premium newsletter, and also has a column at Psychology Today. Todd lives in Maple Ridge, BC, with her husband, one dog, and two cats. 

Useful links:

Salt, C., Morris, P. J., Wilson, D., Lund, E. M., & German, A. J. (2019). Association between life span and body condition in neutered client‐owned dogs. Journal of Veterinary Internal Medicine, 33(1), 89-99. https://doi.org/10.1111/jvim.15367

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